O-glycosylation of nuclear and cytoplasmic proteins by a single ?-N-acetyl-D-glucosamine moiety (O-GlcNAc) is a common post-translational modification that is highly dynamic and fluctuates in response to cellular stimuli. This type of glycosylation has been found on approximately a thousand human proteins to date, and is thought to be nearly as wide-spread and abundant as protein phosphorylation. In fact, O-GlcNAc often competes with protein phosphorylation, and these two modifications have extensive crosstalk in the regulation of signaling, transcription, and the functions of oncogenes and tumor suppressors. The modification appears to play a major role in key pathophysiological conditions including cancer, Alzheimer's disease, and diabetes. Some of the first proteins identified carrying this modification were transcription factors, and it has become clear in the last several years that O-GlcNAc plays a major role in chromatin remodeling and gene expression. The focus of this proposal is to develop site-specific antibodies that can be used as tools in the elucidation of the role that O-GlcNAc plays in epigenetics. We will utilize a new immunogen strategy to develop site-specific O-GlcNac antibodies to five sites of O-GlcNAc modification on the four histone proteins, all of which play a role in chromatin modeling and epigenetics. Consequently, if we are successful, the mAbs generated in this initial study will have an immediate impact on epigenetic research and could have far reaching implications in disease research.